int cash = 1000 // main 不是 module, 所以这里不是全局符号,而是局部变量

fn save(int number):int {
    cash = cash + number
    return cash
}

print('init, cash=', cash, '\n')

save(10)

print('saved 10, cash=', cash, '\n')

save(20)

print('saved 20, cash=', cash, '\n')
